摘要
提出了用低频多模式超声兰姆波定征方法来估计超薄弹性层的纵波声速、横波声速、厚度和密度等参数。这里“超薄”是指材料厚度 h 远小于材料中的声波波长λ,由此导致在时域上材料前后界面的各次回波信号相互混迭。文中采用水浸耦合方式,结合空间波场设计和泄漏兰姆波频域分析方法获取了材料零阶对称与反对称模式兰姆波色散曲线,并以色散特性为基础的零阶对称模式兰姆波定征方法、简化方法、零阶反对称模式兰姆波定征方法和最小二乘意义下以材料色散曲线为基础的反向算法对材料进行了参数估计。文中分析了影响估计准确性的各种因素,研究了低频多模式超声兰姆波定征方法对各材料参数的灵敏度及其在误差传递中的意义。实验结果表明,该方法能够准确估计厚度小到26μm
A low frequency multi mode ultrasonic Lamb wave method suitable for characterizing shear and longitudinal wave velocities, thickness and density of ultra thin elastic layers is presented. By “ultra thin”, we mean that the plate is only a fraction of the ultrasound wavelength. In conjunction with the geometric calculations and leaky Lamb wave frequency domain analysis,the lowest order symmetrical mode Lamb wave method,the appoximate method and the lowest order anti symmetrical mode Lamb wave method are used to characterize the parmeters of the plate coupled by water. The reasons for evaluation error of the parameters and the sensitivity of all methods for different parameters are analyzed. Using a pair of broadband water immersion longitudinal wave with 2MHz center frequency transducers,we have accurately characterize the parameters of aluminum foil with the thickness down to 26μm。
出处
《计量学报》
CSCD
北大核心
2000年第1期59-67,共9页
Acta Metrologica Sinica
基金
中国国家自然科学基金
关键词
超薄弹性层
超声定征
兰姆波
材料测试
Ultra thin elastic layer
Ultrasonic characterization
Lamb wave
Quantity NDE
